1. Field of the Invention
The invention relates to a scheme of using a fixed-size Image Signal Processing unit in digital camera applications, and more particularly to a scheme where the line buffer size is a fraction of the image size of the target sensors, other input devices or sources.
2. Description of the Related Art
Traditionally an ISP (Image Signal Processing unit) needs many line buffers in order to perform the functions like Color Interpolation, zooming/Scaling, etc. The size of the line buffers (and their associated control logic) is typically tailored to the maximum image size of the target sensors. The larger the image is, the bigger the line buffers are and the higher the power consumption and manufacturing cost is. In addition in an ISP of the related art, the maximum image size is limited by the line buffers. These disadvantages severely restrict the desire to offer larger image sizes. To cope with the trend of adapting higher pixel sensors in digital camera applications, a Universal Fixed-Pixel-Size ISP scheme is hereby proposed. This new scheme uses a fixed-size line buffer to handle large images, which usually require large size line buffers in a traditional design. By using this universal ISP scheme there is, theoretically, no limit on the ISP in terms of the maximum image size it can process. Since its native line buffer size is much smaller, this universal ISP scheme has the benefits of smaller die-size, manufacturing cost and lower power consumption.
U.S. Pat. No. 6,870,538 (MacInnis et al) discloses a display engine for processing graphics. The graphics may include multiple graphics layers or windows. The processing elements process two or more graphics layers in parallel to generate blended graphics. This parallelism however differs significantly in nature from the two slice buffers of the invention disclosure. The input (both analog and digital video) for receiving data and the processing elements may be integrated on an IC chip.
U.S. Pat. No. 6,480,631 (So et al.) presents an image processing apparatus for performing rotation, enlargement, reduction, clipping or overlapping processing where each scan line is read fully. The applications are different. The purpose of the proposed invention is to enable a short size ISP to handle large images where a long scan line is divided into many shorter ones.
It should be noted that the above-cited example of the related art does not address the use of fixed-size line buffer for large image sizes of target sensors whereby such fixed-size line buffers are small and have a universal use because there is virtually no maximum limit in the image size that could be processed by such a fixed-size line buffer.